U-Value
0.00
W/m²K
Total R-Value
0.00
m²K/W
Thermal Performance
Poor
Average
Good
Excellent
U-Value Calculator: Measure Thermal Performance of Building Assemblies
What is a U-Value Calculator?
This interactive tool calculates the thermal transmittance (U-Value) of walls, roofs, and other building elements. U-Value measures how effectively a structure insulates – lower values indicate better insulation performance. The calculator helps architects, builders, and homeowners optimise energy efficiency.
Key Features
1. Layer-Based Thermal Analysis
- Add/remove material layers (brick, insulation, drywall, etc.)
- Adjust thickness for each component (in meters or inches)
- Preloaded database of common materials with conductivity values
2. Comprehensive Output Metrics
- U-Value (W/m²K) – Primary insulation performance indicator
- Total R-Value (m²K/W) – Sum of all thermal resistances
- Visual building cross-section diagram
- Colour-coded performance scale (Poor to Excellent)
3. Scientifically Accurate Calculations
- Computes using: U = 1/(Rsi + R1 + R2 + … + Rse)
- Includes surface resistances (internal/external air films)
- Uses real-world material conductivity (λ) values
4. User-Friendly Interface
- Drag-and-drop layer management
- Instant visual feedback
- Mobile-responsive design
- Exportable results
How to Use the Calculator
Step 1: Build Your Assembly
- Click “Add Layer” for each material
- Select from the dropdown (brick, insulation, etc.)
- Enter thickness (e.g., 0.1m for 10cm brick)
Common Material Thicknesses:
| Material | Typical Thickness |
|---|---|
| Brick | 0.1m (4″) |
| Insulation | 0.05-0.15m (2-6″) |
| Drywall | 0.0125m (0.5″) |
Step 2: Set Environmental Factors
- Internal surface resistance (default: 0.13 m²K/W)
- External surface resistance (default: 0.04 m²K/W)
Step 3: Calculate & Interpret Results
Click “Calculate” to view:
- U-Value – Your primary performance metric
- R-Value Breakdown – Individual layer resistances
- Visual Cross-Section – Colour-coded materials
Understanding the Results
U-Value Performance Scale
| U-Value (W/m²K) | Rating |
|---|---|
| < 0.2 | Excellent (Passivhaus standard) |
| 0.2-0.5 | Good (Modern construction) |
| 0.5-1.0 | Average |
| > 1.0 | Poor insulation |
Key Terms Explained
- U-Value: Heat loss per m² per degree temperature difference (Lower = Better)
- R-Value: Thermal resistance (Higher = Better)
- Conductivity (λ): Material’s inherent heat transfer rate
Practical Applications
For Architects & Builders
- Verify compliance with building codes
- Compare different wall assemblies
- Optimise insulation placement
For Homeowners
- Evaluate existing wall performance
- Plan energy-efficient retrofits
- Estimate potential energy savings
Example Calculation
Wall Assembly:
- External Brick (0.1m)
- Insulation (0.1m)
- Drywall (0.0125m)
Results:
- U-Value: 0.35 W/m²K (Good insulation)
- Total R-Value: 2.86 m²K/W
